The major goals of this project are (1) to adapt newly developed methods of embryo culture for teratogenicity studies; (2) to determine the teratogenic potential of certain lipophilic drugs selected on the basis of their strong growth inhibition of cultured mammalian cells; and (3) to evaluate the utility of the embryo culture system for basic studies in developmental biology. In Fy 82 we completed a study showing that the anticonvulsants valproic acid and diphenylhydantoin cause developmental defects in a dose-dependent manner, independent of maternal metabolism. We also adapted two-dimensional electrophoretic techniques and improved silver-staining methods for computer-assisted analysis of embryo proteins. The proteins from a single 10-day mouse embryo can be analyzed by this approach, permitting studies on the appearance of certain identifiable proteins during early stages of development.